Tire treads are required to have high level properties, such as mainly high fuel economy, high abrasion resistance, and high wet grip performance. Various techniques for improving these properties have been examined.
For example, fuel economy is known to be improved by introducing a functional group having an affinity for filler into the polymer chain end; abrasion resistance is known to be improved by using a high molecular weight polymer having a molecular weight of 250,000 or more; and wet grip performance is known to be improved by using a polymer having a high glass transition temperature (Tg).
However, the introduction of a functional group having an affinity for filler, the use of a high molecular weight polymer, and the use of a polymer having a high Tg obtained by increasing the styrene content all unfortunately lead to an increase in the hardness of the rubber composition and deterioration of the processability.
Patent Literature 1 discloses a tire rubber composition having fuel economy, abrasion resistance, and wet grip performance that are improved by incorporation of a liquid resin having a softening point of −20° C. to 45° C. and a specific silica. However, there is still room for improvement in achieving a balanced improvement in these properties while providing good processability.